The structure of known cleaning devices for the grain in harvester-threshers provides a fan, to which an air guiding device is connected on the discharge side, by which means the air stream generated by the fan can be purposely guided to the sifting arrangement.
The use of a cross-flow fan for the cleaning device of a harvester-thresher is shown in German patent document EP-OS 0 385 107. The cross-flow fan consists of a broad, drum-shaped rotor of radial structural form having numerous forward-curved vanes on the housing shell. The suction flow as well as the discharge flow of the fan are transverse to the axial direction of the fan housing. The cross-flow fan used in the harvester-thresher extends over the entire width of the sifting arrangement.
This design of fan has the disadvantageous property that contaminants or grains entering the housing of the cross-flow fan are not automatically discharged. In this way, there is a functional influence due to flow losses, with the consequence that the efficiency of the cleaning device in cross-flow fans installed in harvester-threshers can be detrimentally influenced.